Throughout a subject's lifetime, bones and joints become damaged and worn through normal use and traumatic events. This degradation of the joints involving the articular cartilage and subchondral bone is common to degenerative diseases such as arthritis and results in symptoms including joint pain, tenderness, stiffness, and potential locking of the joint.
Joint replacement arthroplasty is an orthopedic procedure in which the arthritic surface of the joint is replaced with a prosthetic component. It is considered the primary form of treatment to relieve joint pain or dysfunction that may limit mobility. During an arthroplasty procedure, the ends of the bone and articular cartilage are resurfaced (i.e., by cutting the bone) to match the backside of the implant. Current implants used in total knee arthroplasty have flat planar surfaces that connect to the patient's bone, because the current tools used for making the cuts are saws, which are only capable of making flat cuts. Typical femoral implants make use of 5 or 6 planar cuts that conform to the round nature of the condyles. However, in order to preserve the maximum amount of bone, a rounded or curved surface that more closely matches the natural geometry of the femoral condyles would be most effective, but accurately creating these rounded surfaces using conventional manual tools is nearly impossible.
The accurate placement and alignment of an implant is a large factor in determining the success of a joint arthroplasty procedure. Even a slight misalignment there may result in poor wear characteristics, reduced functionality, decreased implant longevity, or a combination of these and other complications.
In order to achieve accurate implant placement and alignment, one must accurately position the cutting tool vis-à-vis the bone prior to making any bone cuts. In some methods, a cutting jig may be used to accurately position and orient a cutting tool such as a saw, drill, or reamer. While in other methods, the cuts may be made using a surgical assist device (e.g., a surgical robot) that controls implements such as a saw, cutter, or reamer. When a surgical assist device is used to make the cuts, the position and orientation of the bone must be known precisely in three-dimensional space (and hence vis-à-vis the surgical assist device) to ensure that the cuts are made in the correct location. Conventional methods of determining spatial orientation and location of a bone require bone registration in a three-dimensional space, either using previously placed fiducial markers or by collecting or digitizing the locations of several points or a digitized matrix on the surface of the bone. The process using previously placed fiducial markers requires an additional surgical operation, and the process of digitizing points on the surface of the bone can be time consuming.
The present applicant in PCT/IB2013/002311 entitled, “SYSTEM AND METHOD FOR REGISTRATION IN ORTHOPAEDIC APPLICATIONS”, which is incorporated herein by reference; provides more efficient methods for a surgeon to rapidly and accurately determine the spatial orientation and location of a bone during orthopedic surgery.
While there have been many advancements in patient specific and personalized implants and orthopaedic surgery, there still exists a need for processes and surgical tools that provide bone surface contours that afford a precise, congruent and also improved fit for surgical implants. There further exists a need for a more precise fitting implant to improve implant acceptance and integration to the patient's bone.